Microstructure Evolution and Thermal Stability of AZ31 Alloy Deformed by Multi-Pass DSR

Experiments were conducted to investigate the microstructural evolution of AZ31 alloy when deformed by multi-pass differential speed rolling (DSR) using the simplest modification of route A passing sequence. Microstructural observations were taken on all three planes of the sample to obtain a three-dimensional view. Based on quantitative microstructural analysis, the counts of the fine DRX grains increased with increasing number of DSR passes, while the fine DRX grains' size was consistent in each pass. These results signified that the refinery process was attributed to dynamic recrystallization. Thermal stability was perceived by examining the evolution in microstructure and microhardness value of the 4-pass DSR sample during isochronal annealing over a range of temperature from 423 to 723 K. The increase in distortion energy with multi-pass DSR resulted in the decrease in critical temperature for the initiation of recrystallization upon annealing at 423 K, which induced an immediate drop in microhardness.